Submerged cryogenic pump with a magnetic linear coupling

ABSTRACT

A pumping system is disclosed for use in pressurizing a cryogenic fluid. The pumping system has a motor, an arm reciprocated by the motor, and a reciprocating pump configured to be submerged in a liquid. The pump includes a piston. The pumping system also has a rod mechanically coupled to the piston and a magnetic coupling configured to reciprocate the rod in response to the reciprocation of the arm. The magnetic coupling includes an outer magnetic portion associated with the arm and an inner magnetic portion associated with the rod.

RELATED APPLICATIONS

This application is a nonprovisional application of provisional U.S. Application No. 62/438,290, filed Dec. 22, 2016, the entire contents of which are expressly incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to a pump and, more particularly, to a submerged cryogenic pump having a magnetic linear coupling.

BACKGROUND

Gaseous fuel powered engines are common in many applications. For example, the engine of a locomotive can be powered by natural gas (or another gaseous fuel) alone or by a mixture of natural gas and diesel fuel. Stationary equipment may also use an engine powered by natural gas. Natural gas may be more abundant and, therefore, less expensive than diesel fuel. In addition, natural gas may burn cleaner in some applications, producing less greenhouse gas.

Natural gas, when used in a mobile application, may be stored in a liquid state onboard the associated machine. This may require the natural gas to be stored at cold temperatures, typically about −100 to −162° C. The liquefied natural gas is then drawn from the tank by gravity and/or by a boost pump, and directed to a high-pressure pump. The high-pressure pump further increases a pressure of the fuel and directs the fuel to the machine's engine. In some applications, the liquid fuel may be gasified prior to injection into the engine and/or mixed with diesel fuel (or another fuel) before combustion.

One problem associated with cryogenic pumps located external to the tank of liquid natural gas involves cooling the pump down before it can be started. To achieve this, external cryogenic pumps use expensive and complicated cool-down circuits and procedures. Additionally, leakage can cause problems for external pumps. External pumps require complicated and expensive seals and bearings capable of preventing leakage. External pumps additionally require expensive and complicated systems for the cold end of the pump handling the liquid fuel. For example, cold-end systems include ventilation, purging, and temperature monitoring.

To reduce cost and complexity, some cryogenic pumps are installed inside the tank and submerged in the liquid natural gas. Submerging an electric motor in high pressure liquid natural gas, however, creates other problems. For example, the electric motor generates heat, boiling the immediately surrounding liquid natural gas. To obtain the benefits of a submerged pump without the complications of submerging an electric motor in liquid, some pumps have a separate compartment inside the tank containing gas. The electric motor is located in this compartment and configured to drive the pump, which is submerged in liquid. For example, the electric motor's rotating shaft can be magnetically coupled to the rotating pump's shaft.

An exemplary pump is disclosed in U.S. Pat. No. 6,213,736 (the '736 patent) that issued to Weisser on Apr. 10, 2001. In particular, the pump of the '736 patent includes a motor housing and a pump housing. An electric motor is within a motor housing, which is filled with a high pressure inert gas. The pump housing contains a pump shaft with an attached impeller. A layer separates the electric motor from the liquid natural gas. A magnetic coupling is embedded in this layer, and as the electric motor shaft turns, the magnetic coupling, in turn, rotates the pump shaft to drive the impeller in the liquid natural gas.

While the pump of the '736 patent may help address some of the difficulties associated with submerging an electric motor in a high pressure cryogenic tank, the rotating components of both the magnetic coupling and the pump shaft present additional problems. For example, rotating bearings are prone to wear, and because they are submerged in high pressure liquid they are difficult to access for service or replacement. Additionally, rotating pumps consume large amounts of energy and have complex and expensive components.

The disclosed pump is directed to overcoming one or more of the problems set forth above and/or elsewhere in the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a pumping system. The pumping system includes a motor, an arm reciprocated by the motor, and a reciprocating pump configured to be submerged in a liquid. The pump includes a piston. The pumping system also includes a rod mechanically coupled to the piston and a magnetic coupling configured to reciprocate the rod in response to the reciprocation of the arm. The magnetic coupling includes an outer magnetic portion associated with the arm and an inner magnetic portion associated with the rod.

In another aspect, the present disclosure is directed to another pumping system. The pumping system includes an electric motor, and the electric motor includes an output shaft rotated by the electric motor. The pumping system also includes a motion converter coupled to the output shaft of the electric motor. The motion converter includes an arm reciprocated by the motion converter in response to rotation of the output shaft of the electric motor. The pumping system also includes a submergible pump, and the submergible pump includes a reciprocating piston connected to a piston rod. The pumping system also includes a linear magnetic coupling configured to reciprocate the piston of the pump in response to reciprocation of the arm of the motion converter. The magnetic coupling includes an outer magnetic portion associated with the arm and an inner magnetic portion associated with the piston rod.

In another aspect, the present disclosure is directed to a method of pumping a liquid. The method includes reciprocating a drive arm located outside of a container of the liquid. The method also includes magnetically coupling a piston rod located inside the container to the drive arm and reciprocating a piston connected to the piston rod and submerged in the liquid in response to reciprocating the drive arm. The method also includes pumping the liquid from the container in response to reciprocating the piston in the liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional and diagrammatic illustration of one embodiment of the pumping apparatus installed in a tank of liquid fuel;

FIG. 2 is an enlarged, cross-sectional, and diagrammatic illustration of a portion of another embodiment of the pumping system; and

FIG. 3 is a cross-sectional and diagrammatic illustration of another embodiment of the pumping apparatus.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary pumping system 10. In the one embodiment, the fluid passing through pumping system 10 is liquefied natural gas (LNG). It is contemplated, however, that pumping system 10 may alternatively or additionally be configured to pressurize and discharge a different cryogenic fluid, if desired. For example, the cryogenic fluid could be liquefied helium, hydrogen, nitrogen, oxygen, or another fluid known in the art.

A motor 16 is configured to reciprocate an arm 18. A reciprocating pump 20 is submerged in a liquid 15, and a magnetic coupling 26 is configured to reciprocate the piston 22 of the reciprocating pump 20 in response to the reciprocation of the arm 18.

Pumping system 10 may be installed within a fuel tank 12. Specifically, pumping system 10 may be installed within a cold well 13. The cold well 13 has a cover 14 and a separation cover 32. The pumping system 10 also includes a motor 16 which may be disposed completely outside of the liquid 15. For example, the motor 16 may be disposed in a space 17 filled with ambient gas 34. The space 17 is disposed between the separation cover 32 and the cold well cover 14. The cold well cover 14 may not hermetically seal this space 17. Rather, it may allow air from the ambient surroundings to enter the space 17.

The motor 16 is configured to reciprocate the arm 18. For example, in a first embodiment illustrated in FIG. 1, the motor 16 has an electromagnetically rotated shaft 42. A motion converter 40 is interposed between the motor 16 and the arm 18. The motion converter 40 is configured to reciprocate the arm 18 in response to rotation of the shaft 42 of the motor 16. The motion converter 40 may be mechanical, for example, such as a scotch-and-yoke mechanism or any other suitable, mechanical motion-converter design. Alternatively the motion converter 40 may be hydraulic, magnetic, electric, or any other suitable motion-converter design.

Referring again to FIG. 1, a separation cover 32 at least partially defines a fluid boundary of the liquid 15. Alternatively, the separation cover 32 may fluidly separate the liquid 15 from an ambient gas 34, such as air. The separation cover 32 and cold well 13 may form a container 33 containing the liquid 15. The separation cover 32 may be composed of any suitable material. For example, the separation cover 32 may be composed of a plastic or composite material. Preferably, the separation cover 32 is composed of material unresponsive to magnetic fields.

The magnetic coupling 26 is configured to reciprocate the rod 24 in response to the reciprocation of the arm 18. The magnetic coupling 26 has an outer magnetic portion 28 and an inner magnetic portion 30. The outer magnetic portion 28 is configured to linearly reciprocate in a direction parallel to an axis 38. Similarly, the inner magnetic portion 30 is configured to linearly reciprocate in a direction parallel to the axis 38.

The outer magnetic portion 28 includes a magnetic material such as a permanent magnet or other material responsive to magnetic fields. Similarly, the inner magnetic portion 30 includes a magnetic material such as a permanent magnet or other material responsive to magnetic fields.

The outer magnetic portion 28 of the magnetic coupling 26 is disposed on a side of the separation cover 32 not submerged in the liquid 15. That is, the outer magnetic portion 28 is disposed outside the liquid 15. The inner magnetic portion 30 of the magnetic coupling 26 is disposed on the opposite side of the separation cover 32, inside the liquid 15. Thus, at least a portion of the separation cover 32 is disposed between the outer magnetic portion 28 and the inner magnetic portion 30 of the magnetic coupling 26.

The separation cover 32 may include a linear guide 36 mechanically engaging at least one of the inner magnetic portion 30 and the outer magnetic portion 28 of the magnetic coupling 26. For example, the linear guide 36 may be an integral portion of the separation cover 32. Alternatively, the linear guide 36 may be a separate component that is attached to the separation cover 32 using any suitable means including fasteners, adhesive, press fit, etc.

The linear guide 36 protrudes into the ambient gas 34 in a direction parallel to the axis 38. The inner magnetic portion 30 of the magnetic coupling 26 is partially received within the linear guide 36. The linear guide 36 is at least partially received within the outer magnetic portion 28 of the magnetic coupling 26. For example, the outer magnetic portion 28 of the magnetic coupling 26 may define a collar slidably engaging an outer surface of the linear guide 36 protruding into the ambient gas 34. And inner magnetic portion 30 may be formed as part of the rod 24.

The linear guide 36 extends along an axis 38 and allows each of the outer magnetic portion 28 and the inner magnetic portion 30 to translate along the axis 38. That is, the linear guide 36 mechanically engages each of the outer magnetic portion 28 and inner magnetic portion 30. The linear guide 36 constrains each magnetic portion 28, 30 against movement in directions other than those parallel to the axis 38. Thus, the linear guide 36, together with the magnetic portions 28, 30, form a linear bearing allowing each of the outer and inner magnetic portions 28, 30 to linearly translate along the axis 38 of the linear guide 36. Any suitable method of reducing friction may be used. For example the magnetic coupling 26 may be disposed in an enclosure (not shown) containing lubricants. Alternatively, rolling bearings such a ball bearings or cylindrical rollers may be disposed between the various surfaces to reduce friction (not shown).

Although FIG. 1 shows the linear guide 36 protruding into the ambient gas 34, the linear guide 36 may, alternatively, protrude into the liquid 15 (not shown). In this embodiment, the outer magnetic portion 28 is still disposed in the ambient gas 34, and the inner magnetic portion 30 is still disposed in the liquid 15. But, the outer magnetic portion 28 is partially received within the linear guide 36 (not shown). And the linear guide 36 is partially received within inner magnetic portion 30 (not shown). For example, the inner magnetic portion 30 of the magnetic coupling 26 may define a collar slidably engaging an inner surface of the linear guide 36 protruding into the liquid 15. And the outer magnetic portion 28 may be formed as part of the rod 24.

In the embodiment illustrated in FIG. 1, the arm 18 is directly attached to the outer magnetic portion 28 and the rod 24 is directly attached to the inner magnetic portion 30. Alternatively, they may not be directly attached to each other. Rather, one or more linkages may associate the outer magnetic portion 28 to the arm 18 and the inner magnetic portion 30 to the rod 24, respectively. And further, any suitable mechanical or hydraulic connection may be used to associate the outer magnetic portion 28 to the arm 18 and the inner magnetic portion 30 to the rod 24, respectively.

Linear guide 36 has an inner surface contacting the liquid 15 and an outer surface contacting the ambient gas 34. The outer surface of the linear guide 36 and the outer magnetic portion 28 may have complementary cross sectional shapes along a plane orthogonal to the axis 38. Similarly, the inner surface of the linear guide 36 and the inner magnetic portion 30 may have complementary cross sectional shapes along a plane orthogonal to the axis 38. For example, the outer surface of the linear guide 36 and the outer magnetic portion 28 may have a cross section defining a circle around the axis 38. Alternatively, they could have any suitable cross section such as e.g., square, rectangular, etc.

In another embodiment, instead of a motor 16 rotating a shaft 42 and a motion converter 40 configured to reciprocate the arm 18 in response to the rotating motion, the motor 16 may be a linear magnetic drive motor (not shown) and may reciprocate the arm 18 directly by electromagnetic drive (not shown). In this embodiment, the motor 16 may have a plurality of electromagnetic coils (not shown), and the coils may encircle the rod 24. The linear magnetic drive motor (not shown) may be combined with the magnetic coupling 26. Alternatively, the outer magnetic portion 28 of the magnetic coupling 26 may be configured to electromagnetically reciprocate the inner magnetic portion 30. The outer magnetic portion 28 may be fixed to the outer surface of the linear guide 36 in the ambient gas 34. The outer magnetic portion 28 may include coils of wire (not shown) encircling the linear guide 36.

Referring again to the embodiment illustrated in FIG. 1, the reciprocating pump 20 is submerged in the liquid 15 and may include a piston 22 received in a piston chamber 23. The piston 22 may be slidably received in the chamber 23. One or more bushings and/or bearings (not shown) may be disposed between the piston 22 and the chamber 23. The reciprocating pump 20 may have one or more inlets 25 fluidly connected to the piston chambers 23. An outlet 46 of a primer pump 44 may be fluidly connected to an inlet 25 of the reciprocating pump 20. The primer pump 44 may be disposed in the fuel tank 12 outside the cold well 13. Alternatively, the primer pump 44 may be disposed inside the cold well 13 (not shown). As is known in the art, a system of one-way valves may be configured to allow intake of liquid 15 during expansions of the piston chamber 23 and pumping of liquid 15 out the fluid discharge line 19 during compression of piston chamber 23.

The reciprocating pump 20 may have one or more pistons 22. As shown in FIG. 1, the reciprocating pump 20 may have a single piston 22. Alternatively, in another embodiment as illustrated in FIG. 2, the pumping system 10 may include a plurality of pistons 22 and a plurality of rods 24. Each rod 24 is configured to reciprocate a single piston 22. A plurality of magnetic couplings 48 couple each rod 24 to the arm 18. A plurality of magnetic outer portions 28 is associated with the arm 18. For example, as shown in FIG. 2, the plurality of magnetic outer portions 28 may be directly attached to the arm 18. Alternatively, the plurality of outer magnetic portions 28 may be mechanically linked to the arm 18 through additional linkages. And further, any suitable mechanical or hydraulic connection may be used to associate the plurality of outer magnetic portions 28 to the arm 18 and the inner magnetic portion 30 to the rod 24, respectively.

Alternatively, the pumping system 10 may include a plurality of electric motors (not shown), and each motor is configured to reciprocate a respective arm 18. In the alternative embodiment with multiple electric motors, a plurality of magnetic couplings 48 may couple each arm 18 to a respective rod 24.

Referring to the embodiment illustrated in FIG. 2, the plurality of magnetic couplings 48 may involve a similar design to the single magnetic coupling 26, described above. Each magnetic coupling 48 has a respective outer magnetic portion 28 and a respective inner magnetic portion 30. The separation cover 32 has a plurality of linear guides 36 formed integrally with the separation cover 32 as a parallel arrangement of adjacent pockets. Each magnetic coupling 48 has a respective linear guide 36 disposed between the outer magnetic portion 28 and the inner magnetic portion 30. Each of the linear guides 36 extends along a respective axis 38. The axes 38 may be parallel to one another. A distance 54 between the outer magnetic portions 28 is measured in a plane orthogonal to the axes 38. A length 60 of the linear guides 36 is measured from a base 36 a to a tip 36 b of the guide 36. The length 60 of the linear guides 36 may be greater than the distance 54 between the outer magnetic portions 28. In some implementations, the length 60 may be more than twice the distance 54 between the outer magnetic portions 28.

Alternatively, the plurality of outer magnetic portions 28 and the plurality of inner magnetic portions 30 may be formed as interleaving plates (not shown). In this embodiment, the distance 54 between the outer magnetic portions 28 is much less than the length 60 of the linear guides 36. The length 60 of the linear guides 36 may be more than three times the distance 54 between the outer magnetic portions 28. As explained above, the distance 54 is measured between pairs of the outer magnetic portions 28. The distance 54, however, may be effectively zero, such that each pair of adjacent inner magnetic portions 30 is built as one inner magnetic portion 30. In this embodiment, the outer magnetic portions 28 interleave the inner magnetic portions 30 with the separation cover 32 disposed between each of the outer magnetic portions 28 and the inner magnetic portions 30. Thus, the separation cover 32 has a plurality of linear guides 36 formed integrally with the separation cover 32 as a parallel arrangement of adjacent pockets receiving the magnetic portions 28, 30.

In another embodiment illustrated in FIG. 3, the reciprocating pump 20 may include a plurality of dual-acting pistons 62. The dual-acting pistons 62 are configured to pump liquid 15 during both portions of the reciprocating motion. The rod 24 is connected to all of the dual-acting pistons 62, for example, with extensions of the rod 24 being connected at points between each pair of dual-acting pistons 62. A system of ports and one-way valves (not shown) may be configured to allow intake of liquid 15 during expansions of the piston chambers 23. The ports and one-way valves (not shown) allow pumping of liquid 15 out the fluid discharge line 19 during compression of piston chambers 23. Alternatively, the pumping system 10 may include a plurality of rods 24. Each rod 24 may be connected to two or more dual-acting pistons 62. For example, each rod 24 may be connected to a respective pair of dual-acting pistons 62.

Alternatively, a single piston 22, similar to the embodiment illustrated in FIG. 1, may be dual-acting (not shown). In this embodiment, the reciprocating pump 20 includes additional ports and one-way valves (not shown) to facilitate the double-action pumping as explained above with reference to FIG. 3.

INDUSTRIAL APPLICABILITY

The disclosed pump finds potential application in any fluid system where high-pressurization of cryogenic fluids is required. For example the disclosed pump may be used in mobile (e.g., locomotive) or stationary (e.g., power generation) applications having an internal combustion engine that consumes the fluid pressurized by the disclosed pump. The disclosed pump finds particular applicability in cryogenic applications, for example in applications having engines that burn LNG fuel. Operation of pumping system 10 will now be explained.

As illustrated in FIG. 1, in one embodiment, the electric motor 16 rotates the shaft 42. The motion converter 40 reciprocates the arm 18 in response to rotation of the shaft 42. The drive arm 18 located outside of the container 33 of liquid 15, however, may be reciprocated by any suitable means. For example, a motor 16 may reciprocate the drive arm 18. The motor 16 may be hydraulic, mechanical (such as an internal combustion engine), or electric.

The arm 18, in turn, reciprocates the outer magnetic portion 28 of the magnetic coupling 26. Magnetic coupling 26 couples the rod 24 located inside the container 33 to the reciprocating drive arm 18. The magnetic coupling 26 reciprocates the piston 22 connected to the rod 24 in response to reciprocating the drive arm 18. Specifically, reciprocating the outer magnetic portion 28 magnetically forces the inner magnetic portion 30 to reciprocate. The inner magnetic portion 30 forces the rod 24 and piston 22 to reciprocate. The piston 22 pumps the liquid 15 out through the fluid discharge line 19 in response to the reciprocating of the piston 22 in the liquid 15.

Liquid 15 is pumped from the tank 12 by the primer pump 44. The primer pump 44 pumps liquid 15 out the outlet 46 of the primer pump 44 and into the inlet 25 of the reciprocating pump 20. The primer pump 44 provides the reciprocating pump 20 with an elevated starting pressure. The reciprocating pump 20 then pumps the liquid 15 out the fluid discharge line 19.

Instead of a rotating motor 16 and motion converter 40, alternatively, the motor 16 may be a linear magnetic drive motor (not shown). In this embodiment, electromagnetic coils may magnetically engage the arm 18. Electric current through the coils produces a magnetic field forcing the arm 18 in one direction. The current is then reversed, producing an opposite magnetic field and forcing the arm 18 in the opposite direction. Thus, alternating the current through electromagnetic coils linearly reciprocates the arm 18.

Alternatively, the outer magnetic portion 28 of the magnetic coupling 26 may electromagnetically reciprocate the inner magnetic portion 30. As noted above, the outer magnetic portion 28 may be fixed to an outer surface of the linear guide 36 in the ambient gas 34. In this embodiment, current alternates in the coils of wire (not shown) encircling the linear guide 36, electromagnetically forcing the inner magnetic portion 30 to reciprocate, as explained above with reference to a linear magnetic drive motor (not shown).

Referring to FIG. 2, the dual-acting pistons 62 pump liquid 15 during both portions of the reciprocating motion. The rod 24 forces the dual-acting pistons 62 in a downward motion and pumps liquid 15 from out of the bottom set of piston chambers 23. The rod 24 then forces the dual-acting pistons 62 in an upward motion and pumps liquid 15 from the top set of piston chambers 23 of the reciprocating pump 20. Although referred to as “bottom” and “top” these terms do not limit the embodiment to this orientation. Rather, the pumping system 10 may be installed in any suitable orientation. For example, the pumping system 10 may be oriented horizontally or in any other suitable direction.

It will be apparent to those skilled in the art that various modifications and variations can be made to the pump of the present disclosure. Other embodiments of the pump will be apparent to those skilled in the art from consideration of the specification and practice of the pump disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A pumping system, comprising: a motor; an arm reciprocated by the motor; a reciprocating pump configured to be submerged in a liquid, the reciprocating pump including a piston; a rod mechanically coupled to the piston; and a magnetic coupling configured to reciprocate the rod in response to the reciprocation of the arm, the magnetic coupling including an outer magnetic portion associated with the arm and an inner magnetic portion associated with the rod.
 2. The pumping system of claim 1, wherein the reciprocating pump is submerged in the liquid, and the motor is disposed completely outside of the liquid.
 3. The pumping system of claim 1, further including a separation cover at least partially defining a fluid boundary of the liquid, wherein the outer magnetic portion of the magnetic coupling is disposed on an outside of the separation cover and the inner magnetic portion of the magnetic coupling is disposed on an inside of the separation cover.
 4. The pumping system of claim 1, further including a separation cover fluidly separating the liquid from an ambient gas, wherein a portion of the separation cover is disposed between the outer magnetic portion and the inner magnetic portion of the magnetic coupling.
 5. The pumping system of claim 4, wherein the separation cover includes a linear guide and the linear guide mechanically engages at least one of the inner magnetic portion and the outer magnetic portion.
 6. The pumping system of claim 4, wherein: the separation cover includes a linear guide; the linear guide protrudes into one of the liquid and an ambient gas; and one of the outer magnetic portion or the inner magnetic portion is at least partially received within the linear guide.
 7. The pumping system of claim 6, wherein the linear guide is at least partially received within the other of the outer magnetic portion and the inner magnetic portion.
 8. The pumping system of claim 1, wherein at least one of the outer magnetic portion and the inner magnetic portion is formed as part of the arm or the rod, respectively.
 9. The pumping system of claim 1, further including: a motion converter interposed between the motor and the arm; the motor including an electromagnetically rotated shaft; and the motion converter being configured to reciprocate the arm in response to rotation of the shaft of the motor.
 10. The pumping system of claim 1, further including a primer pump, the primer pump including an outlet, and the outlet being fluidly connected to the reciprocating pump.
 11. A pumping system, comprising: an electric motor, the electric motor including an output shaft rotated by the electric motor; a motion converter coupled to the output shaft of the electric motor, the motion converter including an arm reciprocated by the motion converter in response to rotation of the output shaft of the electric motor; a submergible pump, the submergible pump including a piston connected to a rod; and a linear magnetic coupling configured to reciprocate the piston of the submergible pump in response to reciprocation of the arm of the motion converter, the linear magnetic coupling including an outer magnetic portion associated with the arm and an inner magnetic portion associated with the rod.
 12. The pumping system of claim 11, wherein at least one of the outer magnetic portion and the inner magnetic portion is formed as part of the arm or the rod, respectively.
 13. The pumping system of claim 11, further including a separation cover configured to at least partially define a fluid boundary of a liquid within which the submergible pump is submerged.
 14. The pumping system of claim 13, wherein the separation cover includes a linear guide and the linear guide mechanically engages at least one of the inner magnetic portion and the outer magnetic portion.
 15. The pumping system of claim 13, wherein: the separation cover includes a linear guide; the linear guide protrudes into one of the liquid and an ambient gas; and one of the outer magnetic portion or the inner magnetic portion is at least partially received within the linear guide.
 16. The pumping system of claim 15, wherein the linear guide is at least partially received within the other of the outer magnetic portion and the inner magnetic portion.
 17. The pumping system of claim 11, wherein at least one of the inner magnetic portion and the outer magnetic portion includes a material responsive to magnetic fields.
 18. The pumping system of claim 11, wherein at least one of the inner magnetic portion and the outer magnetic portion includes a permanent magnet.
 19. The pumping system of claim 11, further comprising a primer pump configured to pump liquid into the submergible pump.
 20. A method of pumping a liquid, comprising: reciprocating a drive arm located outside of a container of the liquid; magnetically coupling a piston rod located inside the container to the drive arm, and reciprocating a piston connected to the piston rod and submerged in the liquid in response to reciprocating the drive arm; and pumping the liquid from the container in response to the reciprocating of the piston in the liquid. 